Initiation of in situ combustion in a secondary recovery operation for petroleum production



United States Patent 3,180,412 INITIATION DE EN SITU CGMBUSTION IN ASEC- ONDARY RECGVERY (BPERATIGN FOR PETRO- LEUM PRODUCTIQ'N Valery N.Bednarski, Bellaire, Robert E. Kunetlra, Houston, and Joseph C. Allen,Bellaire, Tex assignors to Texaco Inc., New York, N.Y., a corporation ofDelawme No Drawing. Filed Aug. 7, 1962, Ser. No. 215,459 12 Claims. (Cl.166-11) This invention relates generally to the treatment of undergroundformations which produce petroleum. More particularly, this inventionrelates to the carrying out of an in situ combustion operation within apermeable underground formation. In accordance with one embodiment, thepractice of this invention is directed to a method of initiating in situcombustion within a permeable underground formation, e.g. by initiatingspontaneous in situ combustion within a petroleum producing or petroleumbearing underground formation.

Various techniques are practiced for the recovery of petroleum fromunderground formations and for the treatment of petroleum producingformations. For the recovery of petroleum from petroleum producingformations, secondary recovery operations which involve water floodingor thermal recovery methods, such as in situ combustion, employing atleast one injection well and at least one production well, have beenproposed.

In a conventional in situ combustion operation after a petroleum bearingformation has been heated to a sufi'iciently high temperature, acombustion-supporting or oxygen-containing gas, such as air oroxygen-enriched air, is introduced into the formation via a well bore. Ahigh temperature zone with a temperature therein in the range 700-2500R, created by the reaction between the thusintroduced oxygen and thecombustible petroleum residues within the formation, such as combustibleresidues resulting from the distillation and/or thermal cracking of thepetroleum originally in place or introduced thereinto, moves outwardlyfrom the well bore into the formation in the direction of flow of hotgaseous combustion products.

Leaving this high temperature zone is a relatively high temperature gasstream at substantially the same temperature. This high temperature gasstream, as it moves outwardly into the formation, loses heat to theformation. By this method, the high temperature reaction zone movesradially outward from the well bore without further direct applicationof heat to the area immediately surrounding the well bore. The distancethe high temperature reaction zone moves outwardly, and accordingly, thevolume of the petroleum producing formation swept by the hightemperature reaction zone, is dependent upon the relative magnitudes ofthe rate of heat generation (the combustion of combustible residues) andthe rate of heat loss to the surrounding formation.

It has been assumed that the following mechanisms are important in anunderground in situ combustion operation for the movement of the hightemperature zone radially outward from the well bore into the petroleumproducing formation. Although the exact mechanism of an in situcombustion is not known definitely, the following sequence of events inan underground in situ combustion operation is postulated and ispresented herein for the purpose of enabling one skilled in the art tounderstand the practice of this invention.

As the high temperature reaction zone approaches a given volume of thepetroleum-containing formation in an in situ combustion operation forthe recovery of petroleum therefrom or for the treatment of saidformation, the temperature of this volume of formation increases. Thisresults in a reduction in the viscosity of the formation liquids(petroleum and brine) therein due to their temperature rise. Thesefluids may then be moved more readily under the influence of the hot gasstream continuously emanating from the high temperature reaction orcombustion zone. As the temperature of this volume of formationcontinues to rise, distillations of the liquids therein begin. Theproducts of these distillations condense in those cooler regions of theformations outward from the high temperature combustion zone in thedirection of gas flow. These distillations continue as the temperaturerises until the heavier components remaining within the petroleumoriginally in place within the formation or introduced thereinto priorto effecting in situ combustion begin to crack or otherwise thermallydecompose, yielding hydrocarbon gases, coke and solid carbonaceousresidues. As the temperature continues to rise and the oxygen content ofthe incoming gas to the given volume of formation increases due to thedepletion of combustible residues in preceding volumes of the formation,a point is reached at which the hot coke or hot combustible residueswill begin to combine chemically with the oxygen with the resutlingrelease of heat to the formation and the gas stream emanating therefrom.This heat is carried away by the onmoving gas stream and also to alimited extent is transferred to the adjacent regions of the formation.When the coke and combustible residues have been burned away, thereremains a volume of substantially liquid-free formation which, unlessotherwise treated, is cooled then gradually by the oncoming relativelycool combustion-supporting gas or air entering the thus-treated givenvolume of the formation via the well here.

One dilficulty in carrying out an in situ combustion operation involvesthe operation of initiating in situ combustion. Various methods havebeen proposed heretofore for initiating in situ combustion. For example,suitable heating means such as electrical heating devices or gas firedbottom hole igniters or heaters suitable for lowering within the borehole opposite the formation wherein in situ combustion is to beinitiated have been employed or suggested. Another method suggested forinitiating in situ combustion involves the introduction of phosphorus orsimilar readily combustible material into the petroleum producingformation to be subjected to in situ combustion.

It is an object of this invention to provide an improved method forinitiating in situ combustion within a permeable underground formation.

Another object of this invention is to provide an improved method ofinitiating spontaneous in situ combustion Within a permeable undergroundformation such as a permeable petroleum producing or petroleum bearingformation.

Still another object of this invention is to provide an improved methodfor carrying out an in situ combustion operation within a permeablepetroleum formation.

Yet another object of this invention is to provide a method of treatingor consolidating a permeable underground formation.

How these and other objects of this invention are accomplished willbecome apparent with reference to the accompanying disclosure. In atleast one embodiment of the practice of this invention, at least one ofthe foregoing objects will be achieved.

In accordance with the practice of this invention, it has beendiscovered that a permeable underground formation is improved and/or aspontaneous in situ combustion operation is initiated therein byintroducing into such a permeable formation an organic unsaturatedcompound, such as an unsaturated aliphatic organic compound comprisingonly carbon, hydrogen and oxygen atoms and containing at least 16 carbonatoms per molecule, and then introducinginto the formation containingsuch an organic compound and into contact with such an organic compound,a gas comprising free oxygen to effect spontaneous insitu combustion ofthe thus-introduced aliphatic organic compound within the permeableformation. More a particularly, it has been found that an oxygenatedaliphatic organic compound, such as an unsaturated long chain fatty acidor an unsaturated long chain fatty alcohol or fat or oil, and theglycerides of unsaturated long chain fatty acids, are suitably employedwithin a permeableunderground formation to eifect initiation of in situcombustion therein; I i V Unsaturated aliphatic compounds comprisingonly carbon, hydrogen and oxygen atoms and containing at least 16 carbonatoms per molecule, which are suitably employed in the practice ofthis'invention, include the various aliphatic long chain olefinic acidsand the corresponding alcohols and esters, such as the triglyceridesthereof. Exemplary unsaturated organic compounds which are suitablyemployed in the practice of this invention include linoleyl alcohol,linolenyl alcohol, linoleyl stearyl alcohol, ricinoleic' alcohol,clupadonyl alcohol and clupadonic acid.

Particularly, useful in the practice of this invention are theunsaturated non-hydrocarbon oils, particularly those oils, so-calleddrying oils'or so-called semi-drying oils, having an iodine numbergreater than 100, especially greater than 130. By .definition, an iodinenumber is the number of grams of iodine absorbed by 100 grams of fat oroil. Those oils having an iodine number below 100 are consideredsubstantially non-drying oils, those oils having aniodine number in therange 100-130 are considered semi-drying oils, and those oils having aniodine number greater than 130 are considered drying oils. Suitablenon-hydrocarbon oils, vegetable and animal (mammal or fish), or mixturesthereof, which may be employed in the practiceof this invention includecorn oil, cottonseed oil, sesame seed oil, sunflower seed oil, soy oil,poppyseed oil, perilla oil, tung oil, oiticica oil, linseed oil and thefish oils, such as herring oil, sardine oil, menhaden oil, whale oil,seal oil, porpoise'body oil, dolphin oil and the like. In generahanyunsaturated non-hydrocarbon oil, animal or vegetable, having an iodinevalue in excess of 130, is suitable in the practice of this invention.For the most part, these oils, such as linseed oil and the like,comprise triglycerides of unsaturated long chain fatty monocarboxylicacids.

Desirably and in accordance with one embodiment of the practice of thisinventio'n,'there is admixed with the non-hydrocarbon oil introducedinto the permeable forniation undergoing treatment a suitable oxidationpro moter. The organic nitrogen bases, such as pyridine, pyrrole,piperidine, aniline anddimethylaniline, are particularly useful asoxidation promoters to pormote a spontaneous in situ combustion inaccordance with this invention.. Desirably also, the unsaturatednon-hydrocarbon oil or unsaturated aliphatic compound introduced intoan' underground formation also contains admixed therewith an oxidationcatalyst or dryer, such as cobalt naphthenate, cobalt tallate, cobaltoctoate, and similar iron or lead riers. However, even with the use of asuitable oxidation promoter and a suitable oxidation. catalyst, it hasbeen found that some oils having a very high iodine numberare notsuitable choices due to the presence of strong acetylenic bonds makingsuch oils not easily oxidizable for the purpose of initiating in situcombustion, e.g. isano oil and compounds thereof. Further, certain 'oilsmay contain natural oxidation inhibitors such as. tocopherols, which arenormally present in vegetable oils and which are removed with the colorbodies in producing refined grades.

In some instances, in accordance with the practice of this invention,particularly when the unsaturated aliphatic 'acid, linoleic acid,linolenic acid, eleostearic acid, eleoorganic compound is a normallysolid material or possesses a viscosity too high for easy injection intoa permeable underground formation, the unsaturated oxidizable mateterialis thinned with or dissolved in or admixed with a suitable solvent ordiluent. Particularly suitable as a carrier is a light hydrocarbonnaphtha, VMP naphtha, Stoddards solvent, and aromatic naphthas such asthe xyleneS, turpentine and the like.

In accordance with one embodiment or feature of this invention, there isincorporated in admixture with the material introduced into thepermeable formation to initiate and to undergo spontaneous combustiontherein a suitable minor amount, in the range 0.25-10% by weight, offinely divided, powdered magnesium or magnesium dust. The powderedmagnesium, once spontaneous in situ combustion has been initiated,greatly increases the amount of heat released and the temperaturegenerated during in situ combustion within the formation undergoingtreatment. 1

In accordance with yet another embodiment of the practice of thisinvention an amount, such as minor amount, of crude petroleum,particularly crude petroleum or a fraction thereof derived from theformation undergoing treatment, may be admixed With the unsaturatedorganic compound or unsaturated non-hydrocarbon oil employed.

Any suitable oxygen-containing fluid such as air, air enriched withoxygen, or substantially pure oxygen may be employed in the practice ofthis invention. Air, preheated to a temperature above F., preferablyabout 200 F. or higher, is particularly suitable for initiating aspontaneous in situ combustion in accordance with this invention. I 1

The practice of this invention is particularly useful when it is desiredto carry out an in situ combustion operation for the recovery ofpetroleum from an underground petroleum producing formation. It is ausual practice when an underground in situ combustion'operation iscontemplated to establish a zone of permeability through the petroleumproducing formation, extending from an injection well to a producingwell. When this zone of permeability has been established, the actual insitu combustion operation can be started. By employing the practiceofthis invention, i.e., by introducing an unsaturated organic compoundordrying oil of the type described herein into the petroleum producingformation immediately adjacent the wall bore and then by passing airtherethrough to establishthis zone of permeability, an operator mayestablish the zone of permeability by flowing air therethrough and mayalso thereby simultaneously initiate the actual in situ combustionoperation so that when the zone of permeability has been established,the in situ combustion operation has also been initiated or is about tobe initiated However, it is not necessary that complete permeability beestablished between an injection well and a producing well, insofar asthe formation adjacent the well bore be found receptive to gasinjection. In this manner, the volume of the producing formationadjacent the well bore can become saturated with injected spontaneouslyignitible mixture especially if there should be a permeability barrierbetween the injection and production wells. 7

From a safety point of view, it is desirable to start combustion Withinthe formation. Without having detailed knowledge of the transitionmechanism, it is known that thechemical mixture used for the spontaneousignition does not remain in liquid state during the time combustion ofthe petroleum takes place. Laboratory experiments in ignition have shownthe presence of a paintlike polymer and no trace of a liquid chemicalmixture in the experimental sand masses. Low temperature oxidation ofspontaneous ignitible mixtures such as disclosed above, converts themixtures from liquid form into a plastic-like solid. Following thissolidification, the reaction continues with the final products beingcarbon monoxide, carbon dioxide and water. By carefully controlling therate of such an exothermic reaction, the in situ petroleum is distilled.

The oxidation of the spontaneous ignitible mixture,

being exothermic, raises its own temperature, that of the surroundingformation, and the petroleum contained therein. It will also raise thetemperature of the injected combustion-supporting gases, e.g., air whichare provided the formation. The injected gases thus heated come incontact with the petroleum present in the formation and begin itsoxidation. By the time the formation has reached some temperaturebelieved to be 400 F. or more, the injected chemical mixture has beenused up but the oxygen saturated fractions of petroleum now begin tooxidize themselves exothermally, raise the temperature further, andsustain combustion as long as enough oxygen is supplied. It is this lastreaction which initiates the in situ combustion. The injected gasesheated by the combustion carry the combustion zone forward, and the hotdry formation left behind preheats other injected gases provided thecombustion zone.

' It is considered essential that the initiation of in situ combustionbe a minimum of a twostage process. The initial rate for combustionsupporting gas injection must be low in order not to cool the injectedchemical mixture and the formation during an induction period whenoxygen is absorbed and higher oxides are formed. Further, to react withsufficient rapidity so that a rapid temperature rise takes place, thechemical mixture must have a large surface area exposed to the oxidizingfluid. Such a large surface area can be only within the formation andnot within the well bore. Therefore, in practice, it is desirable toinject the chemical mixture for at least six inches or more into theformation adjacent the well bore. This amounts to about 11 lbs. oflinseed fatty acids per square foot of well bore area, in addition tothe amount needed to fill the well bore to the top of the formationunder treatment. The initial injection rate of the combustion-supportinggases after ignition and the burn has started is preferably at 2.3 cu.ft. per minute per square foot of area and will vary depending on thedistance the combustion front moves away from the well bore. At thefirst stage of injection, the rate is not more than 1 or /s of the rateafter the burn has started.

In support of the two-stage process described above, the following is anillustrative example: With well head pressure of 30 p.s.i., aspontaneously ignitible chemical mixture was displaced into the wellbore with nitrogen ahead and behind the mixture. Injection of air wasstarted at the rate of approximately 200 M c.f.d. Maximum injectionpressure was 310 p.s.i. after fifteen minutes, which pressure decreasedto 140 psi. in approximately thirty minutes. The injection of air wascontinued with monitoring of adjacent observation wells for temperaturedata and gas analysis. On the following day, the low volume compressorwas taken off stream and replaced by a high volume compressor at a fullcapacity of 1.4 MM c.f.d. The temperature began to rise in an adjacentobservation well within 45 minutes, with a maximum temperature observedof 2172 F. Because of this extreme temperature and several mechanicalfailures, the air injection was discontinued till the well was undercontrol again and the compressor rate was reduced to 850 M c.f.d., withincreased gas production in adjacent pattern wells noticed thereafter.

As another illustration of the practice of the invention, air underpressure was provided the well bore to displace fluid therefrom and toestablish air permeability and/or receptivity in the formation. Asindicated by a flow meter that adequate air permeability had beenestablished, the well was bled down from approximately 600 p.s.i.g. toatmospheric pressure. Immediately thereafter, approximately 800 poundsof linseed fatty acids were introduced into the well bore. Thesechemicals were displaced from the tubing inserted into the well bore by60 cu. ft. of nitrogen injected immediately behind the chemicals therebyproviding a cushion of inert atmosphere.

On the following day, during the initial period and several hoursthereafter, an attempt was made to hold the flow rate of air injectionat about 5400 cu. ft. per hour, the rate being established on the basisof laboratory experiments. Two days later on, the well was bled down forindications of in situ combustion, the effects of which were indicatedby thermocouple readings above 200 F. and gas analysis with a C0concentration of 3%. Also, the strange odor of cracked and partiallyoxidized hydrocarbons characteristic of in situ combustion was noted inthe efiluent gases. All these phenomenon were determined to besuiiicient evidence that spontaneous combustion had taken place.Injection of air was resumed immediately, with the combustion raisingthe temperature up to about 1150 F.

Injection of air at increasing rates, up to 19,500 cu. ft. per hour, wascontinued for the three following days, the injection being interruptedperiodically and the well allowed to cool when temperatures in excess of300 F. were noted.

On the following day, with a flowing pressure of /3 p.s.i.g., the wellwas shut in, and the pressure stabilized at /2 p.s.i.g. Gas sampleBurrell analysis showed 28.4% as CO and 1% as 0 with production to beresumed at a later date.

Also, the following examples further illustrate the practice of thisinvention.

EXAMPLE NO. 1

An in situ combustion test cell, provided with thermocouple leadstherein and having wall heaters which were controlled to approximateadiabatic operation, was packed to within 4-5 inches of the top with38.4 lbs. of an admixture made up of 40 lbs. of Galveston sand and 2.4lbs. of 20 A.P.I. West Columbia crude. Thereafter 500 ml. of linseedfatty acids (predominantly a mixture of oleic, linoleic, and linolenicacids) and 5 ml. of 6% cobalt naphthenate, as an oxidation catalyst, and5 ml. of dimethylaniline, as a combustion promoter, was poured in thetop. The head of the test cell was then bolted and while still in thevertical position, air pressure was applied to the test cell sufficientto force the resulting catalyzed admixture of linseed fatty acids intothe sand-oil mixture. The test cell was then placed in a horizontalposition.

Compressed air at p.s.i.g. was allowed to enterthe test cell and a valveat the exit gas line of the cell was used to regulate the rate of airflow therethrough. A flow meter and a wet test meter in series were usedto measure the rate of flow of exit gas from the cell. Initially, duringthe test, the air flow rate was set at 0.035 cubic feet per minute(c.f.m.). Within 15 minutes, that portion of the cell (Section 1)nearest the entry of air began to register a rising temperature on thetemperature recorder.

which also contained a thermocouple, to maintain the outside and insidetemperatures the same. Any unbalance in temperature was registered as anunbalance on a microammeter. By this means the temperature differencebetween the outside and inside wall -of the test cell probably did notexceed 7 F. The same procedure was used with the remainder of the testcell sections (total of fourteen sections), but no heat was applieduntil the inside of test cell section was hotter than the outside.

' After 30 minutes, the air flow rate was increased to 0.055 c.f.m.About three hours later, the air flow rate was increased to 0.070 c.f.m.This last air flow rate increase showed an increase in the rate oftemperature rise Heat was then applied to the outside of Sec-' tion 1 ofthe test cell with an electric heating element,

within the test cell and by this time temperatures in excess of 400 F.were indicated within Section 2 of the test cell. Theair flow rate wasthen increased to 0.103 c.f.m. and subsequently to 0.200 c;f.m. andmaintained at this rate for the remainder of the test (total of about 14hrs.). Sections 1 and 2 of the test cell indicated temperatures thereinin excess of 1000 F. The rest of the test sections indicatedtemperatures between 780 F. and 910. F. During this experiment, thenormal yield of recovered oil was also obtained.

EXAMPLE NO. 2

mixture comprising 95% by" volume linseed fatty acids plus by volumecrude oil (20 A.P.I. West Colum: bia); (2) an admixture comprising 90%linseed fatty acids and crude oil; (3) an admixture comprising 80%linseed fatty acids and 20% crude oil; (4) an admixture comprising 17.6%crude oil, 70.6% linseed fatty acids and 18.8% gum turpentine; (5) anadmixture comprising 11.8% gum turpentine and 88.2% crude oil.

EXAMPLE No. 3

In the test the same experimental procedure set forth with rspect toExample '1 was employed, save that 500 m1. of raw linseed oil to whichhad been added 5 ml. of

6% cobalt naphthenate and 5 ml. of dimethylaniline were employed. Inthis test after ignition, the in situ combustion proceeded in a normalmanner and'within a relatively shorttime (8 hours) Section 4 of the testcell exhibited a temperature of 940 F. At this time the test wasconcluded since it was indicated that spontaneous in situ combustion hadoccurred and that the in situ combustion process was well underway.

Anexamination of the test data observed with respect to the tests setforth in Examples 1, 2 and 3 indicated that at the beginning ofthe'spontaneous in situ combustion operation, an excessive amount of airflow might remove heat from the sand mass undergoing test more rapidlythan the heat couldbe generated therein by spontaneous combustion. Asthe temperature increased, however, e.g'., above about 400 F.,preferably at about 600 F the rate of air flow into the test cell couldbe substantially'increased, such as about twofold that used at 500 F.,about threefold that used at about 400 F; and about fourfold, that usedat about 200 F. r

. EXAMPLE NO.

Further spontaneousin situ combustion tests employing commerciallyavailable high iodine number (inexcess of 130) fatty oils, acids andalcohols Were carried out. From these tests it was observed that thelinseed fatty acids, primarily an admixture comprising oleic, linoleieand linolenic acids, were the most reactive of these materials tested.Temperatures in the test cell 'in the range, 240260 F. were reachedeasily with air at normal pressures and within a relatively short time,about 10 hours. "Of the unsaturated fatty alcohols, best results withrespect to the initiation of spontaneous in situ combustion wereobtained with those alcohols which have as an impurity its correspondingacid. The fish oils tested also exhibited in situ spontaneouscombustion. The following materials were tested: linseed fatty acids(Iod.

165), putty oil (Iod. No. 150-180), LCP fish oil (Iod. No. 170-195), C1unsaturatedalcohols (Iod. N0. 173), C2042 unsaturated alcohols (Iod. No.181).

i 20 API crude+.01% vana I in situ combustion.

(3) *Waterwhite distilled linseed 'acids 98% by Wt. 7 Typicalproperties:

Sa'po'nification value 197-204 Iodine value 180-min. Acid value 197-204N,N-dimethylaniline 1% by Wt. 6% Cobalt'naphthenate 1% by wt.

EXAMPLE 5 In another test a Dewar-flask was packed with absorbent cottonsoaked with catalyzed raw linseed oil. During the test the temperatureWithin the flask after a period of about '60 hours of air flowtherethrough rose to a value much above 400 'F. and cotton Within theflask was 7 badly charred.

7 EXAMPLE, NO. 6

Additional tests employing substantially pure oxygen instead of air andvarious sand pack compositions were carried out in a manner similar tothat set forth in connection with Example 5. The sand pack-compositionstested for'the initiation of spontaneous in situ combustion are setforth in accompanying Table I.

Table l e charge Galvcstonsand, grams Boiled linseed oil; mr Raw linseedoil, ml 6% Co naphthenate, m1 Dirnethylaniline (DMA) Gum turpentine, ml

naphthenate, ml 20 API erude+2% ammonium vanadate, ml...

Testsi 3land 6 did not give evidence of spontaneous Two of the sandpacks (catalyzed raw linseed with turpentine and boiled linseed oil withg'um turpentine) gave in situcombustion temperatures well above 200 F;When the more volatile components thereof had vaporized and formed anexplosive mixture within the test cell, in both cases the vacuum flaskscontainingthe sand packs were shattered upon explosion.

Further experimentation has revealed taht the follow ing mixtures willignite readily for in situ combustion when injected into formationscontaining crude oil.

(1) Raw linseed oil M--. 98% by Wt. Typical properties: a v

Saponification value 189495 Iodine value 170-190 Acid-ivalue 4 max; VN,N-dir nethylaniline 1% by wt. (com- I I f mercial). 6% Cobaltnaphthenate 1%by Wt. (drier grade).

(2),, Same as above except that aniline is substituted forN,N-dimethylaniline.

fatty (4) Same as above except that aniline is substituted forN,N,-dirnethylaniline. I

On the other hand, there'has been no indication of in situ combustionwhen the following mixtures wererused,

. leading to the presumption of lack of ignition thereof.

*No. 180 min), chinawood fatty'acids (Iod. No. 158- I a Percent (1')Isano oil 100 (2) Isano oil-.. 98 N,N-dimethylaniline V 1 Cobaltnaphthenate' 1 A high iodine value oil'containing an acetylenic triplebond The practice of this invention is particularly applicable to an insitu combustion operation employing a plurality of wells, that is, atleast one injection well and at least one production well. In accordancewith one practice of this invention adapted to an in situ combustionopera tion employing a plurality of Wells, an air injection well and anoil production well, a fracture is created between these Wells,preferably by means of hydraulic fracturing, thereby creating a zone ofhigh permeability between these Wells. This high permeability zone isthen partially filled with a spontaneous in situ combustion agent inaccordance with this invention and spontaneous in situ combustioninitiated therein.

The subject invention may be practiced also in connection with a singleWell for well remedial treatment since by following the practice of thisinvention, sandy or incompetent formations are consolidated. Moreover,the practice of this invention is particularly applicable to a singlewell in situ combustion treatment operation as disclosed in coassignedPatent No. 2,906,340, issued to Gerhard Herzog on September 29, 1959,the disclosure of which patent is incorporated herein by this reference.In this patent, there is described a single well in situ combustionoperation as a remedial treatment to increase the productivity and/orpermeability of an underground petroleum producing orpetroleum-containing formation, wherein is disclosed the introduction ofa hydrocarbon oil into an injection Well prior to the introduction of anoXidizable liquid mixture.

Although considerable emphasis has been placed in this disclosure on theuse of unsaturated fatty acid compounds (linseed oil, linseed oil acidsand the like) and unsaturated aliphatic compounds containing at least 16carbon atoms, there may be employed in the practice of this inventionother materials which suitably undergo spontaneous combustion, such asunsaturated aliphatic compounds and hydrocarbons containing as low ascarbon atoms per molecule and which may contain in addition to carbonand hydrogen atoms other atoms such as nitrogen and/ or sulfur and/ orphosphorus and/ or oxygen.

In a recapitulation of the preceding disclosure, reference is made tothe copending, coassigned application for patent, Serial No. 863,044,filed December 30, 1959, by Charles D. Woodward and Billy H. Towell, nowUS. Patent No. 3,126,960, and to the coassigned Patent No. 3,019,838,issued February 6, 1961 to Don L. Harlan, Joel A. Battle, Jr. and JosephC. Allen, the disclosures of which are incorporated herein. In summary,the disclosures of the above-identified application and the patent aredirected to a method for the completion of a well bore involving thesetting of casing and production tubing housed in the casing and with apacker between the tubing and casing, the end of the tubing beingadjacent the bottom of the bore hole, displacing oil in the Well borewith water so that the oil-water interface is above the final packerseat location, pulling the tubing and packer up the bore hole andsetting the packer below the oil-water interface (cg. approximately 50ft. above the petroleum bearing formation) with the open end of thetubing being located adjacent the bottom of the petroleum bearingformation, after which the casing-tubing annulus is filled with waterunder pressure to help hold the packer seated. To initiate ignition, airreceptivity and/or permeability are established, after which the wellbore is purged with nitrogen and then ignition chemicals are displacedto the formation with nitrogen followed by air injection at reducedrates, increased later after ignition has been accomplished to continuein situ combustion.

In a representative operation, a minimum air inje tion rate of 1,000 Ms.c.f.d. to establish receptivity and/ or permeability in the formationwill be maintained until the injection pressure has been stabilized forat least one half hour, stabilization being considered to have beenreached it? when the pressure decrease is not more than 20 p.s.i.g. perhour.

Thereafter, two volumes of nitrogen will be injected into the Well bore,the volume of the nitrogen being determined by the capacity of theproduction tubing string and the capacity of the well bore annularspacing below the packer.

Then a volume of ignition chemicals are displaced into the well borewith nitrogen, the volume of chemicals being used at an average rate ofone 55 gallon drum for each 3 to 4 feet of pay thickness, while thevolume of nitrogen used to displaced the chemicals into the well boreand to purge the chemicals into the well bore will depend upon thepressure required for each well. A sufficient volume of nitrogen will beinjected to establish receptivity of the nitrogen to the formation at adecreaseing pressure gradient.

Then, to initiate ignition and in situ combustion air injection will beat the rate of 200 M c.f.d. for 8 hours, 300 M c.f.d. for 8 hours andthen, as required, an increase to about 1.5 million cubic feet per dayat an injection pressure of 200 p.s.i.

It should be noted that in a Z-directional line drive projection, theremay be a departure from linearity, and altering the injection rates inthe several injection wells can overcome or mitigate such possibleundesirable behavior, and a better sweep efliciency would be obtained.

As will be apparent to those skilled in the art, other substitutions andchanges are possible in the practice of this invention without departingfrom the spirit or scope thereof. i

We claim:

1. In a thermal recovery method of treating a permeable petroleumbearing underground formation penetrated by an injection well and aproduction well, the steps including establishing a zone of receptivityin said formation adjacent said injection Well by flowing airtherethrough purging said injection well by an inert gas, introducinginto said formation through said injection well a liquid mixturecomprising an unsaturated aliphatic organic compound comprising onlycarbon, hydrogen and oxygen atoms and containing at least 16 carbonatoms per molecule and an organic nitrogen base as an oxidation promoterby displacement by an inert gas, subse-' quently introducing a fluidinto said formation containing the liquid mixture introduced thereincomprising free oxygen for spontaneous reaction with said unsaturatedaliphatic organic compound therein raising the temperature of saidformation adjacent said injection well for ignition thereof withconversion of said mixture introduced into said formation from liquidform, and thereafter flowing air through said zone of receptivity insaid formation at a substantially higher rate than that of thesubsequently introduced fluid to efiect in situ combustion therein.

2. A method in accordance with claim 1 wherein said unsaturatedaliphatic organic compound is selected from the group consisting offatty acids, fatty alcohols and fatty oils.

3. In the method of initiating in situ combustion in a ermeabiepetroleum bearing underground formation traversed by a bore hole, thesteps including establishing a zone of receptivity in said formation byflowing air therethrough, providing an inert gas to said formationthrough said bore hole, introducing into said formation a fluid mixtureincluding an unsaturated non-hydrocarbon oil having an iodine number inexcess of and an organic nitrogen base as an oxidation promoter bydisplacement by an inert gas, subsequently introducing into saidformation through said bore hole a stream of an oxygencontaining gas fora period of time sufiicient to increase the temperature of saidunderground formation for ignition with conversion of the introducedmixture from liquid form, and flowing air into said zone of rece tivityat a substantially higher rate than that of the subsequently therein. l1

Ill;

introduced stream of gas to initiate in situ combustion of petroleumwithin said formation, said organic nitrogen base beingdimethylaniliner1 I 4. In the method of initiating in situ combustion with in apermeable petroleum bearing underground formation traversed by a'borehole, the steps comprising establishing a Zone of receptivity in saidunderground formation 1 adjacent said bore hole by flowing airtherethrough, providing an inert gas to said bore hole, introducing intosaid formation through said bore hole a liquid mixture comprising apetroleum solvent, a drying oil having an iodine number in excess of100, and an organic nitrogen base as an oxidation promoter bydisplacement by an inert gas, andsubsequently introducing air' at alower rate into contact with said drying oil of said mixture intro-.duced into said formation for a period of time suflicient to eflectconversion of said mixture introduced into said formation from liquidform and then at a higher rate to-effect ignition of the petroleum insaid formation and thereby to initiate in situ combustion within saidformation. 1 a

5. In the method as defined in claim 4, said solvent being turpentine,said drying oil being linseed oil, said organic nitrogen base beingdimethylaniline, and said inert gas being nitrogen.

, ,6. The -method of initiating in situ combustion within a permeablepetroleum bearing underground formation a penetrated byatleast aninjection well comprising forming a zone of receptivity in saidunderground formation by flowing air therethrough, purging saidinjection well by an inert gas, introducing into said formation a liquid'mixture comprising an unsaturated aliphatic organic compound containingat least 16 carbon atoms per molecule,

an organic nitrogen base for the promotion of oxidation,

7 a petroleumsolvent, and an oxidation catalyst by displacement by aninert gas, subsequently introducing through said injection well intosaid formation exposed to said liquid mixture a gaseous streamcontaining free oxygen for a period of time sufiicient to increase thetemperature of thetreated formation by oxidation of said organiccompound therein with conversion from liquid form for ignition of thepetroleum insa'id formation, and

flowing air through said zone of receptivity in said forma-' tion at asubstantially higher rate than that of the subsequently introducedgaseous stream for in situ combustion 7. In the method as defined inclaim 6, said unsaturated aliphaticorganic compound being selectedfrom'the groupconsisting of fatty acids, fatty alcohols and fatty oils,

' said petroleum solvent being turpentine, said oxidation catalyst beingcobalt naphthenateyand said inert gas corn-- prising nitrogen. a I

I 8. Inthe method of initiating in situ combustion in a permeablepetroleum bearing underground formation penetrated by an injection welland a production well, wherein prior to the initiation of the in situcombustion there is introduced into i said formation through saidinjection well a liquid mixture of an unsaturated aliphaticnon-hydrocarbon compound containing only carbon, hydrogen and oxygenandhaving'at least 16 carbon atoms said petroleum in the formation.

per molecule together with an oxygenation catalyst, said liquid mixturebeing capable'of spontaneous oxidative reaction with air at thetemperature and pressure of said underground formation with theliberation of heat, and wherein this'is followed by the introduction ofair through said injection well into said formation intocontactwith isaid liquid mixture for effecting in situ combustion of petroleum withinsaid formation, the improvement which comprises, following theintroduction of said liquid mixture,'introducing a gaseous fluidselected from the group consisting of air and air diluted with an inertgas at a lower rate effective to produce a controlled reaction with saidliquid mixture to effect the conversion of said un-' saturated compoundto mainly gaseous reaction products without explosive violence whileliberating insuflicient heat to initiate in situ combustion of saidpetroleum but at thesame time liberating suflicient heat to raise thetemperature of petroleum and the immediately surround-:

ing formation adjacent the inlet end of said formation to a degree atwhich further temperature rise of said petroleum and the immediatelysurrounding formation occurs upon continued passage of said gaseousfluidtherethrough,,andthen continuing the passage of a gaseous fluid selectedfrom said group 'at a higher rate to sweep said gaseousreaction productsresulting from the reaction of substantially all of said introducedunsaturated compound from said inlet endof the said formation -be-: forethetemperature of petroleum therein reaches in situ combustiontemperature, then continuing the flow 'of said gaseous fluid at" a rateto initiate in situ'combustion of '9. In the method in accordance withclaim 8, the step of introducing a'quantity of a hydrocarbon oil throughsaid inject-ionwell into said formation prior to the introduction ofsaid liquid mixture.

10.1 In the method in accordance with claim 8, the steps of purging saidinjection well by an inert gas prior to. and following the introductionof said liquid mixture;

11. In the method in accordance with claim 8, the flow I of said gaseousfluid initiating in situ combustion being at a rate providing 2.3 cubicfeet per minute per square foot of area adjacent said inlet end exposedto the heat of reaction of said introduced unsaturated compound, saidlower rate beingjin the range of to /5 thereof; V

12. In the methodin accordance withclaim 8, said lower rate being in therange of 200,000 to 300,000 cubic feet per day, the rate of flow'of saidgaseous fluid initiat ing in situ combustion beingin the range ofv fourto five times as much. a 1

1. IN A THERMAL RECOVERY METHOD OF TREATING A PERMEABLE PETROLEUMBEARING UNDERGROUND FORMATION PENETRATED BY AN INJECTION WELL AND APRODUCTION WELL, THE STEPS INCLUDING ESTABLISHING A ZONE OF RECEPTIVITYIN SAID FORMATION ADJACENT SAID INJECTION WELL BY FLOWING AIRTHERETHROUGH PURGING SAID INJECTION WELL BY AN INERT GAS, INTRODUCINGINTO SAID FORMATION THROUGH SAID INJECTION WELL A LIQUID MIXTURECOMPRISING AN UNSATURATED ALIPHATIC ORGANIC COMPOUND COMPRISING ONLYCARBON, HYDROGEN AND OXYGEN ATOMS AND CONTAINING AT LEAST 16 CARBONATOMS PER MOLECULE AND AN ORGANIC NITROGEN BASE AS AN OXIDATION PROMOTERBY DISPLACEMENT BY AN INERT GAS, SUBSEQUENTLY INTRODUCING A FLUID INTOSAID FORMATIN CONTAINING THE LIQUID MIXTURE INTRODUCED THEREINCOMPRISING FREE OXYGEN FOR SPONTANEOUS REACTION WITH SAID UNSATURATEDALIPHATIC ORGANIC COMPOUND THEREIN RAISING THE TEMPERATURE OF SAIDFORMATION ADJACENT SAID INJECTION WELL FOR IGNITION THEREOF WITHCONVERSION OF SAID MIXTURE INTRODUCED INTO SAID FORMATION FROM LIQUIDFORM, AND THEREAFTER FLOWING AIR THROUGH SAID ZONE OF RECEPTIVITY INSAID FORMATION AT A SUBSTANTIALLY HIGHER RATE THAN THAT OF THESUBSEQUENTLY INTRODUCED FLUID TO EFFECT IN SITU COMBUSTION THEREIN.